Must Have Applications

Free and open source program uninstaller. Can remove large amounts of unwanted applications quickly. .

HexChat is an IRC client based on XChat for Linux , but unlike XChat it’s completely free for both Windows and Unix-like systems.
HexChat was originally called XChat-WDK which in turn was a successor of freakschat.

Features

Easy to use and customizable interface
Cross-platform on Windows, OS X, and Unix-like OSes
Highly scriptable with Python and Perl
Translated in multiple languages
Fully open source and actively developed
Multi-network with auto-connect, join, and identify
Spellcheck, Proxies, SASL, DCC support and more

Convert videos to formats that work on your mobile phone, tablet, TV media player, game console, computer, or web browser.

The Sysinternals Troubleshooting Utilities have been rolled up into a single Suite of tools. This file contains the individual troubleshooting tools and help files. It does not contain non-troubleshooting tools like the BSOD Screen Saver or NotMyFault.

The Suite is a bundling of the following selected Sysinternals Utilities:

AccessChk
AccessEnum
AdExplorer
AdRestore
Autologon
Autoruns
BgInfo
CacheSet
ClockRes
Contig
Coreinfo
Ctrl2Cap
DebugView
Desktops
Disk2vhd
DiskExt
DiskMon
DiskView
Disk Usage (DU)
EFSDump
Handle
Hex2dec
Junction
LDMDump
ListDLLs
LiveKd
LoadOrder
LogonSessions
NTFSInfo
PageDefrag
PendMoves
PipeList
PortMon
ProcDump
Process Explorer
Process Monitor
ProcFeatures
PsExec
PsFile
PsGetSid
PsInfo
PsKill
PsList
PsLoggedOn
PsLogList
PsPasswd
PsService
PsShutdown
PsSuspend
RegDelNull
RegJump
RootkitRevealer
SDelete
ShareEnum
ShellRunas
SigCheck
Streams
Strings
Sync
TCPView
VMMap
VolumeID
WhoIs
WinObj
ZoomIt

Windows system utilities to maximize productivity.

The qBittorrent project aims to provide a Free Software alternative to µTorrent. Additionally, qBittorrent runs and provides the same features on all major platforms (Linux, Mac OS X, Windows, OS/2, FreeBSD).

qBittorrent is based on the Qt toolkit and libtorrent-rasterbar library.

Features

Polished µTorrent-like User Interface

Well-integrated and extensible Search Engine
Simultaneous search in most famous BitTorrent search sites
Per-category-specific search requests (e.g. Books, Music, Movies)

All Bittorrent extensions
DHT, Peer Exchange, Full encryption, Magnet/BitComet URIs, ...

Remote control through a Web user interface
Nearly identical to the regular UI, all in Ajax

Advanced control over trackers, peers and torrents
Torrents queueing and prioritizing
Torrent content selection and prioritizing

Natively integrated: When Downloads Completes Options (no need for additional script or plug-in)
Exit, Suspend, Hibernate, Shutdown

UPnP / NAT-PMP port forwarding support

Available in ~41 languages (Unicode support)

Torrent creation tool

Advanced RSS support with download filters (inc. regex)

Bandwidth scheduler

IP Filtering (eMule and PeerGuardian compatible)

IPv6 compliant

Sequential downloading (aka "Download in order")

Available on most platforms: Linux, Mac OS X, Windows, OS/2, FreeBSD

Calibre is a free and open source e-book library management application made by users, for users. Many languages, designed around the concept of the logical book, i.e., a single entry in your library that may correspond to actual e-book files in several formats.

Calibre can sort the books in your library by title, author, date added, date published, size, rating, or series, along with extra metadata such as tags and personal comments. You can easily search your book collection for a particular book, based on any of this information. Calibre can also go onto the internet to find online books based on existing title/author or ISBN information.

In addition, Calibre also:
-syncs to your ebook reader
-downloads news from the internet and converts it into ebook form
-offers a ebook viewer that can display all major ebook formats

Features:

Library Management
E-book conversion
Syncing to e-book reader devices
Downloading news from the web and converting it into e-book form
Built-in e-book viewer
Content server for online access to your book collection
E-book editor for the major e-book formats

File and folder lookup tool that searches across local, removable, and network mapped drives.

Firefox is a cross-platform web browser developed by the Mozilla Foundation. Firefox is a popular product, used in over 50 languages and available for Windows, macOS, Linux, Android and iOS.